1. Field of the Invention
This invention relates generally to filters for filtering debris, gravel, hydrocarbons, and other contaminants from water flowing into runoff drains.
2. Prior Art
Runoff drains are provided in streets, parking lots, gas stations, and highways for draining water runoff. Some runoff drains are provided with internal filters for preventing debris, hydrocarbons, and other contaminants from entering waterways.
My prior U.S. Pat. No. 5,958,226 discloses a runoff drain filter sized to be positioned inside a runoff drain. It includes a top debris tray detachably positioned within a bottom media tray. Each tray includes a peripheral trough surrounding a central overflow opening. The top tray is shorter in height than the bottom tray, so that a filter media receiving chamber is defined between the top tray and the bottom tray. Filter medium is positioned in the filter medium receiving chamber. In a first embodiment, the bottom surfaces of the top and bottom trays are perforated. In a second embodiment, the bottom of the top tray and the inner wall of the bottom tray are perforated. In either embodiment, water flowing into the filter is distributed around the top trough, passed through the perforated surface of the top tray, the filter medium, the perforated surface of the bottom tray, and into the runoff drain. Hydrocarbons and other contaminants are filtered by the filter medium. Large particles and debris are collected in the trough of the top tray. The filter may be cleaned by lifting out the top tray, shaking out the debris, and replacing it in the bottom tray. However, the perforated surface of the top tray is relatively small, so that it may quickly clog when a large amount of debris flows into the filter. The top tray can be removed by lifting on its handle.
My prior U.S. Pat. No. 6,217,757 discloses another runoff drain filter with an annular debris trough, and concentric tubular vertical screens surrounding a central overflow opening in the annular trough. A filter media is positioned between the screens. As debris accumulate in the trough, the vertical screens will start clogging at the bottom, but the top will remain clear for continuing to filter the runoff.
U.S. Pat. No, 5,720,574 to Barella discloses a filter for being positioned inside a runoff drain. It includes a peripheral trough surrounding a central overflow opening. A set of cartridges containing filter medium are positioned in the trough. Water flowing into the drain is distributed around the trough, and passes through the cartridges before exiting through a screen on the bottom of the trough. When water flow is high, excess water overflows through the central opening without passing through the cartridges. However, gravel, leaves, and other debris accumulate on top of the cartridges and block water flow, so that a worker must reach in and dig them out by band, which is slow and time consuming. The horizontal screen has a relatively small surface area which may quickly clog when the inflow of debris is high. There is no handle for lifting the filter from the drain. U.S. Pat. No. 5,632,889 to Tharp discloses a similar filter.
U.S. Pat. No. 5,480,254 to Autry et al. discloses a runoff drain filter that comprises a box with porous vertical walls and an opening on the bottom. It is wider than a runoff drain for being positioned on top of and across it; it cannot be installed inside the runoff drain. Runoff water is filtered by the porous vertical walls as it flows through the filter and into the drain. The filter element of crushed stone is housed in a single chamber, but is too coarse to filter out anything but the largest pieces of debris. The filter element cannot be removed for cleaning or replacement.
Each of the prior art filters is provided with a single tray or container for collecting debris and contaminants. When the container is filled with heavy debris, such as sand and gravel from construction site runoff, the container may be much too heavy for an average person to lift out of the runoff drain. In that case, it can only be emptied by laboriously digging out the debris with a small shovel.
The objectives of the present runoff drain filter are:
to filter out debris, sand, gravel, hydrocarbons, and other contaminants from water runoff flowing into a runoff drain;
to collect a large amount of debris;
to prolong filtering time;
to continue unimpeded filtering even after collecting a large amount of debris;
to be impossible to clog;
to have filter cartridges which are easily replaced;
to have cartridges which are easily lifted from the drain by an average person;
to be usable for filtering large particles without becoming clogged; and
to be also usable for filtering small particles and pollutants.
Further objectives of the present invention will become apparent from a consideration of the drawings and ensuing description.
A runoff drain filter is comprised of a tray for being supported inside a runoff drain. A plurality of separately removable cartridges are supported by the tray and aligned with holes in the tray. Each cartridge is comprised of a bucket and an insert. The insert is comprised of a central overflow tube centered in the bucket by a vented annular top plate and an annular bottom plate. Runoff pouring into the tray is directed into each bucket through the vented annular top plate. The runoff is filtered by a perforated tube which is part of the central overflow tube before it is discharged through an open bottom of the central overflow tube. Debris and contaminants are collected in the buckets. The total capacity of the filter is divided among the separately removable cartridges to enable a filled cartridge to be more easily lifted by an average person.